Venetian blinds, with an adjustable opening mode having more flexibility than the roller type window shade, have long been accepted for window covering. They are commonly made in the form of mini-blinds, with 1" wide slats, which have become the single most popular such device. With the exception of several rather complex and consequently expensive variants, the adjustment of slat angle in venetian blinds is uniform from top to bottom. While this is tolerable, considering the overall ease of use, a more selective adjustment control is desirable. It would be appreciated if the user could block the lower portion of the blind for privacy while leaving the top portion open for light or, to the opposite, open the lower portion for a better view while closing the upper portion to a morning or afternoon sun.
It is the object of the present invention to accomplish such control in an inexpensive manner and furthermore, in a manner which can be applied to virtually any venetian type blind. A further object is to make the installation of such control readily removable so that the blind can be restored to normal operation at any time the user should wish.
These objects are met in the present invention by shortening the slat tilt control ladder between upper and lower portions of the slat array so that the lower slats are tilted to an open position while the upper slats are more or less closed closed. With the tilt of the slat members biased in this manner, closing the lower slats tilts the upper slats to an open position. Intermediate positions adapt the blind to varied lighting conditions and are also useful.